Throughout the Cold War, the United States operated the notorious School of the Americas at Ft. Gulick in the Panama Canal Zone. This article from the Council on Hemispheric Affairs explains how this training center contributed to some of the worst human-rights abuses on the part of Latin American dictatorships.
As the article mentions, the U.S. Congress is in a position to start making amends. After the school was strengthened and renamed (WHINSEC) by the second Bush Administration, Congress came close to shutting it down last year. Meanwhile, Congress is currently debating whether to publish the names of its graduates. (June 26 update: Congress has given preliminary approval to this amendment, mostly along party lines.)
Understanding SOA/WHINSEC is important to understanding world-wide concerns about U.S. military interventions.